1. Field of Invention
This invention relates generally to lorgnettes which when held by a user having defective vision before his eyes, then improves the user's vision, and more particularly to an emergency lorgnette for this purpose having two pairs of lenses of different optical power, the user selecting that pair which best accommodates his eyes to the reading matter or the object being viewed.
2. Status of Prior Art
The Kanbar U.S. Pat. No.3,876,294 discloses a lensless ophthalmic device serving as a temporary or emergency substitute for any type of prescription eyeglasses, making it possible for most individuals having defective sight, without regard to the optical nature of the defect, to see more clearly. The device is constituted by a molded plate having a profile defining a pair of eyepieces joined to a nose piece, each eyepiece having a pattern of pin holes therein adapted to project a clear image of the object viewed on the related eye of the wearer. The spacings between holes in the pattern is such that when the plate is placed against the eyes, the eye is unable to resolve the hole pattern and the holes in each eyepiece appear to merge to form one large opening.
The drawback of a lensless device of the type shown in my prior patent is that what the viewer sees is observed through a pin hole grid that substantially reduces the amount of light received by the eyes. This makes it difficult to see under dim light conditions.
An individual whose eyesight is defective, can achieve the optimum degree of correction by using eyeglasses whose lenses are prescribed to correct for myopia (nearsightedness), hyperopia (farsightedness), astigmatism or whatever other visual disorder requires corrections.
The lenses of prescription spectacles, when serving to correct the focus of the eye for near and far distances are convex. The diopter of a convex lens is the measure of its power and this offers a simple method for prescribing spectacles appropriate to the defect to be corrected.
Those who suffer from defective eyesight and have to wear prescription eyeglasses to see more clearly are often rendered helpless if the eyeglasses are misplaced or broken. But in many instances as a matter of personal vanity, a woman having defective eyesight will not when going to a restaurant or to any other place away from home, bring along her spectacles, for wearing spectacles is regarded as unglamorous. This presents a problem, for when dining in a fashionable restaurant, this woman must consult a menu, and without her prescription glasses she may be unable to do so.
While the pinhole lorgnette of the type disclosed in the above-identified Kanbar patent, makes it possible for an individual having defective vision to read a menu, should the restaurant be dimly lit, as is often the case, the loss of light produced by the pinholes makes it difficult to then read the menu. The same problem is experienced when this individual wishes to consult a telephone directory or to read any other printed text under poor light conditions.
Design Pat. No. Design 206,910 to Lueddike shows a one piece lorgnette formed of transparent material having a pair of convex lenses. While this design patent does not indicate how this pair of lenses correct the wearer's visual defect, should these lenses be prescription lenses, they would be useable only by the individual for whom the lorgnette is prescribed.
The Avad U.S. Pat. No. 5,037,192 discloses an emergency eyeglass formed of a flat clear plastic plate of credit card size molded to define a pair of optical lenses "having diopter power", the card having a cut out between the lenses to accommodate the nose of the user. The Avad device is intended for use by an individual in an emergency situation in which the individual does not have his prescription eyeglasses available.
While Avad does not identify the diopter power of the lenses, whatever power they may have, this will render these lenses corrective only for some visual defects, but not for others. Hence many individuals will not be able to see more clearly when using the Avad device. For example, the Avad device may be effective when the individual using it is near-sighted, but may be much less effective if the individual is farsighted.